Title

the problem link

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells). The island doesn’t have “lakes” (water inside that isn’t connected to the water around the island). One cell is a square with side length 1. The grid is rectangular, width and height don’t exceed 100. Determine the perimeter of the island.

Example:

[[0,1,0,0], [1,1,1,0], [0,1,0,0], [1,1,0,0]]

Answer: 16 Explanation: The perimeter is the 16 yellow stripes in the image below:

题目大意：给个地图，求岛屿的边长和，这就需要点数学智商了，我的好像不够。。。。

Solution

//cpp:
class Solution {
public:
	int islandPerimeter(vector<vector<int>>& grid) {
		int count = 0, repeat = 0;
		for (int i = 0; i < grid.size(); i++) {
			for (int j = 0; j < grid[i].size(); j++) {
				if (grid[i][j] == 1) {
					count++;
					if (i > 0 && grid[i - 1][j] == 1) repeat++;
					if (j > 0 && grid[i][j - 1] == 1) repeat++;
				}
			}
		}
		return 4 * count - 2 * repeat;
	}
};